Method and system for enhanced radiation detection

ABSTRACT

A radiation detection sensor includes a radiation detector that is segmented into an array of mapping elements, or detectors. The mapping elements may be micro-disposed, such that individual mapping elements are substantially thermally isolated from each other and comprise pixels of a visual thermal energy map. The mapping elements of the radiation detector may be minimally connected to adjacent radiation detectors, or the mapping elements may be substantially physically isolated from each other.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/005,671 filed Dec. 6, 2004 entitled “Method and System forEnhanced Radiation Detection” by Jorge Roman et al. Priority of thefiling date of the prior application is hereby claimed, and thedisclosure of the prior application is hereby incorporated by reference.

BACKGROUND

1. Field

The present invention relates generally to radiation detection systemsand in particular to enhanced resolution radiation detection.

2. Description of the Related Art

Detection of radiation that is emitted from objects and is outside ofthe visible spectrum can provide useful information. For example,detection systems have been developed for sensing infrared radiation(IR) from an object or source in a target space. Infrared imagers, alsocalled thermal imagers, are instruments that create images of heatinstead of light, by converting radiated IR energy to a correspondingmap of temperatures or radiance. IR sensing applications includingtemperature measurement and mapping, forest fire sensing andsuppression, and surveillance.

Thermal imaging systems are generally constructed from a variety ofdifferent types of infrared detectors. Infrared detectors can beclassified as cooled or uncooled. Uncooled detectors include thermalsensors that generate a change in a physical parameter of the detector,such as resistance, due to a change in detector temperature resultingfrom incident infrared radiation. Cooled detectors include infraredsensors where the change in the physical parameter of the sensor is dueto a photoelectron interaction within the material of the sensor.

To detect thermal variation across a target space, thermal imagingsystems often use two-dimensional arrays of infrared detectors. In atypical thermal imaging system, the radiation from a target space objectwill be focused onto a detector array. Electronic or mechanical scannersare generally employed to measure the radiation detected by eachdetector in the array and thereby produce a two-dimensional displaycorresponding to a thermal map of the object being imaged. The size andactive area of each sensor in the array limits the spatial resolution ofthe imaging system. Likewise, the need to make electrical connection tothe individual detectors, for example to measure a resistance change,can increase system complexity as well as impose constraints on theminimum size for the detectors.

Liquid crystal materials can change color in response to receivedthermal energy. Typically, liquid crystal materials are used forindicating thermal change and are supplied in film form, or as acoating. In a typical application, a liquid crystal film or coating maybe applied to a radiating surface of an object for direct sensing ofsurface temperature by observing variations in color across the liquidcrystal material as a result of the object's surface temperatureprofile.

Because liquid crystal films are not made up of individual detectors,they do not have the drawback of being limited by a minimum detectorsize. Also, because liquid crystal films are directly viewed, there isnot the need for electrical connections to detect changes in physicalparameters. However, liquid crystal films suffer from poor resolutionbecause the thermal energy “bleeds” across the film or coating.

Thus, a need exists for improved methods and apparatus for the detectionof radiation emitted from objects. Other problems with the prior art notdescribed above can also be overcome using the teachings of the presentinvention, as would be readily apparent to one of ordinary skill in theart after reading this disclosure.

SUMMARY

Embodiments disclosed herein address the above stated need of improvingdetection of radiation emitted from an object. In accordance with theinvention, a radiation detection sensor includes a radiation detectorthat is segmented into an array of mapping elements, or detectors. Themapping elements are substantially thermally isolated from each otherand comprise pixels of a visual thermal energy map. The mapping elementsof the radiation detector may be minimally connected to adjacentradiation detectors, or the mapping elements may be substantiallyphysically isolated from each other. The mapping elements may bemicro-disposed, such that individual mapping elements are substantiallythermally isolated from each other and comprise pixels of a visualthermal energy map, or material may be removed to provide thesegmentation and isolation.

In one exemplary embodiment of a sensor, a focal plane array comprisinga radiation detector with mapping elements formed by a substrate withthermal detection material disposed upon it. In this embodiment, theradiation detector is segmented into an array of mapping elements byvoids in the substrate and the corresponding thermal detection material.The voids can be formed by removing portions of the substrate anddetection material to create “perforations” between adjacent detectorsto minimize thermal conduction between detectors within the array. Thevoids can also be formed by removing portions of the detection materialand leaving the underlying substrate substantially unchanged.Alternatively, the voids can be formed using deposition or lithographictechniques so that detection material is disposed or deposited on thesubstrate only in areas of interest, thereby forming the array ofmapping elements, also referred to herein as detectors. The voidsbetween adjacent detectors serves to minimizes thermal conductionbetween detectors within the array.

Various techniques may be used to remove the thermal material and thesubstrate. For example, a laser may be used to remove the thermalmaterial after it has been deposited on the substrate. Alternatively, amask may be placed on the substrate and thermal detection material canbe disposed onto the substrate and mask in a deposition or platingoperation. The mask is then removed, thereby removing the thermalmaterial in the mask area and leaving behind the voids that define themapping elements. In addition, various techniques, such asphotolithographic techniques and techniques as used in semiconductorfabrication, may also be utilized to form the mapping elements.

In still another exemplary embodiment of a focal plane array sensor,detectors are located in different planes of the sensor. For example,one array of detectors may be located in one plane and another array ofdetectors may be located in another plane across the array. The twoplanes may be substantially parallel to each other. Thermal isolationbetween adjacent detectors may be achieved if adjacent detectors are indifferent planes.

The focal plane arrays do not need to include a substrate. For example,the mapping elements of the detector can be formed of a thermal detectormaterial and an absorber material, with the absorber material disposedacross the thermal detector material in a segmented fashion to definethe mapping elements. Alternatively, thermal detector material can bedisposed on absorber material in a segmented fashion to define themapping elements. In other words, a continuous material is simply ameans for supporting a segmented layer such that the continuous materialand the segmented layer together provide a focal plane array withmapping elements such that individual mapping elements are substantiallythermally isolated from each other and comprise pixels of a visualthermal energy map. Thus, a sensor can be constructed with one or theother of the elements, i.e. thermal detector material or absorbermaterial, performing the supporting function and the other materialbeing segmented.

In addition, while some embodiments describe examples of detectors asincluding a thermal detector material and an absorber material, theembodiments are not limited to this type of construction. That is,exemplary detectors map one form of energy to another form of energy toprovide a visual thermal energy map. For example, a detector may be anydevice that performs the function of mapping thermal energy to a visualdisplay.

In one exemplary embodiment, a radiation detection sensor includes athermal conversion material that converts incident radiation into heatenergy and also includes a plurality of mapping elements, or detectors,each of which receives heat energy from the thermal conversion materialin proximity to the mapping element. A thermal map is producedcorresponding to the incident radiation energy received by the sensor,in accordance with sufficiently limited lateral energy dispersionbetween detectors.

In another exemplary embodiment, a radiation detection sensor includesmapping elements formed with a substrate, and protruding from the topsurface of the substrate is an array of columns. The sensor includesradiation detectors having a radiation sensitive layer, such as aradiation sensitive film, and a thermal conversion material, such as anabsorber, that may be disposed upon a top surface of the individualcolumns within the array. The columns provide thermal isolation betweenthe radiation detectors and the substrate. Spatial separation of columnswithin the array provide thermal and radiant isolation between theradiation detectors upon the tops of individual columns. An array ofradiation detectors allows detection, or identification, of theradiation emitted from an object.

In one exemplary embodiment, the radiation detection sensor has asubstrate that is planar. In other embodiments, the substrate may beconstructed to be a non-planar shape or constructed of a pliablematerial so that it can be formed to non-planar shapes. For example, thesubstrate may be shaped or formed to be concave, convex, or othercomplex surfaces.

In another exemplary embodiment, the radiation detectors include aradiation sensitive layer comprised of a thermochromic liquid crystal(TLC) material and include a thermal conversion material comprised of aninfrared absorbing layer disposed on a top most surface. For example,the absorbing layer may comprise black cupric oxide. In this embodiment,the absorbing layer converts radiation that impinges on it into heatthat is detected by the TLC radiation sensitive layer.

The radiation detection sensor may also include thermal elements thatare used to control the temperature of the substrate. The substrate maybe heated or cooled, for example, using heaters/thermoelectric coolersso as to enable biasing of the sensor. In another embodiment, theradiation detection sensor may include thermal shunts. The thermalshunts may be placed at various locations in the radiation detectionsensor, for example, the thermal shunts may be located between thesubstrate and the base of the columns in the array. The thermal shuntsmay also be located between a source of radiation input and the array ofradiation detectors, for example, in the optics used to focus an imageof the radiation source onto the array, or in a plane on top of theradiation detectors. The thermal shunts may also be located between theradiation detectors and the column tops.

The thermal shunts may be controllably operable so as to provide a highthermal conductance path, or a low thermal conductance path, between thesubstrate and the column/sensor element combination or between thesource of the radiation and detectors. In one embodiment the thermalshunts may be constructed from thermoelectric cooler material, such as,bismuth telluride or other types of solid state heating/coolingmaterials. In addition, thermal shunts may be magnetically orelectrically alignable carbon nanotubes and ferro-fluids.

The columns of the radiation detection sensor can be various shapes andsizes. For example, in one embodiment the columns are cylinders. Inanother embodiment a top surface of the column is larger than the baseof the column thereby maximizing the amount of incoming radiation thatimpinges upon an individual detector. The columns can have any desiredcross section, for example, circular, oval, square, rectangular, or anyother multi-sided polygon shape desired. In addition, there may bemultiple detectors supported by a single column or multiple columns maysupport a single detector. For example, a detector may have a sphericalshape and there may be three columns supporting the detector. Otherconfigurations of detectors and support structures may also be used.

An exemplary embodiment of a radiation detection system uses a radiationdetection sensor that has multiple radiation mapping elements orradiation detectors. The sensor receives radiated energy emitted by anobject and converts the received energy into thermal energy. Then areceived thermal energy map of the object is produced.

In one exemplary embodiment, a radiation detection system may include afocal plane array that has a substrate and a plurality of columnsprotruding from the substrate. Radiation detectors are disposed on topsof the plurality of columns thereby creating an array of radiationdetectors. In one embodiment the radiation detectors include athermochromic liquid crystal material. The system also may includecollection optics that focus radiation emitted from an object onto thefocal plane array. The system may include imaging optics that focus animage of the focal plane array radiation detectors onto an imagingsensor. The imaging sensor may be a video camera, for example, a CCDcamera. The system may also include an illumination source thatilluminates the focal plane array. The system may also include anenvironmental control unit. For example, the environmental control unitmay operate to maintain a substrate of the focal plane array at adesired temperature, or vacuum, or humidity level or control anycombination of environmental characteristics including magnetic fieldand electric field environments. The system may also include an imageprocessor configured to accept an output from the imaging sensor.

A null sensor radiation detection system may include a focal plane arraythat includes a substrate and a plurality of mapping elements disposedin an array on the substrate, wherein radiation detectors are a layer onthe mapping elements, thereby creating an array of radiation detectors.The system may also include collection optics that focus radiationemitted from an object onto the focal plane array. In addition, thesystem may include an illumination source configured to illuminate thefocal plane array, and imaging optics that focus an image of the arrayof detectors onto an imaging sensor. An image processor may beconfigured to accept and analyze the output from the image sensor andgenerate a command for a controllable radiation source. The command forthe controllable radiation source may cause the controllable radiationsource to output radiation that is directed to the focal plane array andmaintains the detectors at a predetermined value.

A controllable radiation source may also be used to output a knownradiation directed to the focal plane array to characterize thesensitivity and response of detectors with the focal plane array. Forexample, the focal plane array may be exposed to a constant radiationlevel, a step change in radiation level, a gradient radiation level, orother variable radiation level. In addition, a target with a knownradiation profile may be exposed to the focal plane array. For example atarget “shutter” may be placed in front of, or in the entrance pupil, ofthe radiation detector system and thereby be exposed to the focal planearray. The performance of the detectors within the focal plane arraywhen exposed to a known radiation can be evaluated. For example, theperformance characteristics of the detectors, such as sensitivity andresponse to a step, or varying radiation input can be evaluated.

In another exemplary embodiment of a radiation detection system a targetillumination source illuminates, or “paints” an object. Radiationreflected from the object may then be collected by collection optics andfocused onto the focal plane array. The target illumination source maybe tunable. For example, the target illumination source may includeoptics or controls to shape the spectrum of the radiation output by thetarget illumination source. In another example, the target illuminationsource may include multiple sources, each of which outputs a desiredspectrum of radiation. The output of the target illumination source maybe mixed, or combined, in any desired combination so that a desiredoutput spectrum is achieved. In this manner the object may be paintedwith radiation of a desired spectral content which may improve thedetection of specific objects.

Other features and advantages of the present invention should beapparent from the following description of exemplary embodiments, whichillustrate, by way of example, aspects of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an embodiment of a radiationdetector system constructed in accordance with the invention.

FIG. 2 is plan view of an exemplary embodiment of a portion of a focalplane array.

FIG. 3 is a cross sectional view of one embodiment of a focal planearray.

FIG. 4 is a cross sectional view of another embodiment of a focal planearray.

FIG. 5 is a plan view of a focal plane array 16 illustrating anotherembodiment of a focal plane array.

FIG. 6 is a cross sectional view of an embodiment of a focal planearray.

FIG. 7 is a cross sectional view of another embodiment of a focal planearray.

FIG. 8 is a cross sectional view of yet another embodiment of a focalplane array.

FIG. 9 is an elevation view of another embodiment of a focal planearray.

FIG. 10 is a plan view of an embodiment of a focal plane array providingincreased active area.

FIG. 11 is an isometric illustration of an exemplary embodiment of afocal plane array 16.

FIG. 12 is a cross sectional view of one embodiment of a focal planearray such as illustrated in FIG. 11.

FIG. 13 is a cross sectional view of another embodiment of a focal planearray constructed in accordance with the invention.

FIG. 14 is a cross sectional view of yet another embodiment of a focalplane array.

FIG. 15 is a schematic diagram illustrating additional aspects of aportion of the focal plane array.

FIG. 16 is a cross sectional view of another embodiment of a focal planearray.

FIG. 17 is a schematic diagram illustrating additional aspects of aportion of the focal plane array.

FIG. 18 is a schematic diagram illustrating an exemplary arrangement ofcomponents of a radiation detector constructed in accordance with theinvention.

FIG. 19 is a schematic diagram illustrating additional detail of anexemplary arrangement of imaging components that may be used in aradiation detector constructed in accordance with the invention.

FIG. 20 is a schematic diagram illustrating another exemplaryarrangement of components of a radiation detector.

FIG. 21 is a block diagram of another embodiment of a radiationdetection system in accordance with the invention.

FIG. 22 is a schematic diagram illustrating an exemplary design of afocal plane array.

FIG. 23 is a schematic diagram illustrating another exemplary design ofa focal plane array.

FIG. 24 is a schematic diagram illustrating yet another exemplary designof a focal plane array.

FIG. 25A is a schematic diagram of a support column with a circularcross section.

FIG. 25B is a schematic diagram of another support column with acircular cross section.

FIG. 25C is a schematic diagram of yet another support column.

FIG. 25D is a schematic diagram of still another embodiment of a supportcolumn.

FIG. 26 is an schematic diagram of an embodiment of a non-planar focalplane array.

FIG. 27 is an schematic diagram of another embodiment of a non-planarfocal plane array.

FIG. 28 is an schematic diagram of an yet another embodiment of anon-planar focal plane array.

FIG. 29 is an schematic diagram of still another embodiment of anon-planar focal plane array.

FIG. 30 is a block diagram of an embodiment of an environmental controlunit.

FIG. 31 is a block diagram of a null sensor arrangement.

FIG. 32 is a block diagram of another embodiment of a radiation detectorsystem.

FIG. 33 is a schematic diagram illustrating another embodiment of aradiation detection system.

FIG. 34 is a flow chart illustrating detection of radiation from anobject.

FIG. 35 is an elevation view of another embodiment of a focal planearray.

DETAILED DESCRIPTION

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Embodiment described herein are “exemplary”and are not necessarily to be construed as preferred or advantageousover other embodiments.

In accordance with the invention, a radiation detection sensor includesa radiation detector that is segmented into an array of mappingelements, also referred to herein as detectors. The mapping elements aresubstantially thermally isolated from each other and comprise pixels ofa visual thermal energy map. The radiation detector receives thermalenergy and generates the visual thermal energy map, which is provided bythe sensor for viewing. The mapping elements of the radiation detectormay be minimally connected to adjacent mapping elements, or the mappingelements may be substantially physically isolated from each other. Themapping elements may be micro-disposed, such that individual mappingelements are substantially thermally isolated from each other andcomprise pixels of a visual thermal energy map.

Techniques and apparatus for improved radiation detection are described.FIG. 1 is an exemplary block diagram illustrating an embodiment of aradiation detector system 10 constructed in accordance with theinvention. As shown in FIG. 1, radiation emitted from an object 12 iscollected by collection optics 14 and focused onto a focal plane array16. An illumination source 18 provides illumination of the focal planearray 16 and an optical image of the focal plane array 16 is focused byimaging optics 20 onto an image sensor 22.

The object 12 may be any object that emits radiation. For example, theobject 12 may emit infrared, visible, ultraviolet, Terahertz, or otherradiation. The radiation emitted from the source 12 is collected byappropriate collection optics 14. The collection optics 14 may differdepending on the type of radiation desired to be detected. For example,if it is desired to detect infrared radiation, then the collectionoptics 14 may be configured so as to pass infrared radiation and blockother types of radiation. The collection optics 14 can be configured topass any desired spectrum of radiation that can be focused by theoptical means. For example, if the radiation detection system 10 isconfigured to be operated in a dark environment, such as at night, thecollection optics 14 may be configured to focus all radiation onto thefocal plane array 16.

The collection optics 14 are well known in the art, and may be one ormore of any number of lenses or other optic components. The collectionoptics 14 produce a focused image of the object 12 onto the focal planearray 16, so that focal plane array 16 may sense the radiant fluxemitted by the object 12. The collection optics 14 may include lensesthat are made of various types of optical glasses, and optical coatings,to achieve a desired spectral transmittance. The collection optics 14may also include other types of optical material so that a desiredoverall spectral transmittance of the collection optics 14 is achieved.In other words, the collection optics 14 may include any device thatfocuses radiation within a desired spectrum onto the focal plane array16. For example, for infrared radiation in the range of approximately0.6 to 21 microns, Zinc Selenium (Zn Se) lenses and windows withantireflective coatings may be used. In addition, the lenses may be ofthe type piano convex for image formation upon the focal plane array.The collection optics 14 may also include other optical devices, suchas, Fresnel lenses, zone plates, pin hole apertures and fish-eye lenses,biconvex, biconcave, and piano concave.

The focal plane array 16, as described in further detail below, includesa plurality of radiation detectors onto which radiation from the object12 is detected. Each detector within the focal plane array 16 senses aportion of the field of view of the radiation detection system 10. Inother words, each individual detector in the focal plane array 16represents a single pixel, or mapping element, of the radiationdetection system 10.

As described further below, in one embodiment of the focal plane array16, when exposed to radiation, the individual radiation detectors in thearray change color in response to the intensity of the radiationincident upon the individual detector. The illumination source 18illuminates the focal plane array 16 with minimal disturbance to theincoming radiation. For example, in the path between the illuminationsource 18 and the focal plane array may be placed an optional filter 21.The filter may be configured to block radiation from the illuminationsource that the detectors within the focal plane array would sense,while passing other radiation. For example, if the detectors aresensitive to heat, the filter 21 may be configured to block infraredradiation but pass other radiation. In one embodiment, the filter 21 maybe constructed of glass which substantially blocks infrared radiation soas to minimize any disturbance, or influence, of the illumination sourceupon the focal plane array detectors that sense infrared radiation,while still allowing the focal plane array to be imaged through thefilter 21.

The illumination source 18 may have a broad or a narrow spectral output.In addition, the illumination source may be tunable. In one embodiment,the illumination source 18 may be constructed of one or more narrow bandsources so as to be able to enhance specific response ranges of thedetectors. That is, the illumination source may have one or more narrowband sources, such as narrow band LEDs, that output a spectrum matchedto a specific spectral range of interest in the spectrum of athermochromic liquid crystal (TLC) detector. For example, a TLC detectormay change color from red to yellow to green to blue as its temperatureincreases in response to radiation incident on an absorber that isconverted to thermal energy. If a particular radiance level,corresponding to a particular color of the TLC, is of interest, then theillumination source may be selected or “tuned” to that particular color.In this way, as the TLC changes to the particular color the sensitivityof the readout of the TLC may be improved. For example, if the radiancelevel of interest corresponds to a TLC color of green, then theillumination source may be tuned to green. When the TLC is red or yellowor blue, the TLC readout will be low because the source illuminating theTLC does not include these colors. When the TLC changes to green the TLCreadout will increase because the illumination source matches the TLCcolor. Because the TLC readout increases, the sensitivity or the abilityto detect small color changes, and corresponding radiation levelchanges, is improved.

The imaging optics 20 focus an image of the focal plane array 16detectors onto an image sensor 22. The imaging optics 20 are well knownin the art, and may be one or more of any number of lenses or otheroptic components. The imaging optics 20 produce a focused image of thedetectors of the focal plane array 16 onto the image sensor 22. Theimage sensor 22 then produces an output corresponding to an image of thedetectors of the focal plane array 16. The image sensor 22 may be, forexample, a camera such as a CCD camera. The image produced by the CCDcamera may be displayed to a user, or it may be provided to an imageprocessor for further processing.

FIG. 2 is plan view of an exemplary embodiment of a portion of a focalplane array 16. As shown in FIG. 2, a substrate 24 is coated with athermal detector material 262 (illustrated as a shaded region). In eachcase, the focal plane array includes a plurality of mapping elements, Inthe example illustrated in FIG. 2, regions 264 of the substrate 24 andthermal detector material 262 are removed thereby producing an array ofdetectors, or mapping elements, 266. Removal of the substrate 24 andthermal detector material 262 produce a “perforated” pattern between thedetectors 266 within the array. In the example illustrated in FIG. 26the detectors 266 are shows as rectangular shapes, but the detectors maybe any desired shape, for example, triangular, pentagonal, octagonal, orany other desired shape.

As illustrated in FIG. 2, removal of regions 264 of the substrate 24 andthermal detector material 262 provide thermal isolation between theindividual detectors 266. In the example shown, individual detectors 266are minimally connected to adjacent detectors 266 at their corners 268.While there may be some thermal conductivity between adjacent detectors266 by way of the material at the connecting corners, the thermalconductivity can be reduced to a desirable level by minimizing the areaof the connection between the detectors 266. In another embodiment, thethermal detector material 262 between adjacent detectors 266 is removedentirely, with the underlying substrate 24 remaining. In this way, theunderlying substrate 24 provides mechanical support for the detectors266 and also provides thermal isolation between adjacent detectors 266.Selection of different materials for the substrate 24 can providedifferent levels of thermal isolation as desired.

In one example, perforations define detectors, or pixels, that areapproximately 500 microns in diameter or diagonal size. It isanticipated that the detectors may be much smaller, such as about 50microns, depending on operating environment, desired energy spectrum ofdetection, and desired application. The perforations may be producedusing a cutting source such as a laser that “burns” the substrate andthermal material to create the voids that provide the segmentation.Smaller detector size may be achieved, in part, using improved power andcontrol of the laser to minimize the detector size. The size of thedetector, or pixel, selected for a particular sensor may vary dependingon factors such as the sensor operating environment, including thewavelength of the light and/or preconditioning light being used.

The focal plane array can be made of a substrate and detectors. In oneexample, the detectors include TLC and an absorber. The detector may beapplied directly to the substrate, or it may be attached to thesubstrate using a binder material. In one example, the layers of thefocal plane array 16 are deposited, or sprayed on, by starting with asubstrate, such as polystyrene, of about 25 microns thickness, then alayer of binder such as PVA, of about 10 microns thickness, next a layerof TLC of about 10 to 30 microns thickness, and then an absorber layercoating of about 10 to 20 microns thickness.

In the example shown in FIG. 2, the perforation pattern is comprised ofsquare cuts, i.e., four cuts to define a generally square-shapeddetector, or pixel. The pattern, however, could also be provided inother patterns, for example, triangular (three sided) pixels, oroctagonal (eight-sided), or any other desired shape. The particularshape may be selected to achieve or provide a desire characteristic. Forexample, octagonal detectors may provide improved thermal isolationbetween adjacent detectors, or pixels, at their corners oversquare-shaped detectors and therefore might be preferred.

The perforations thermally isolate the detectors, or pixels, therebysubstantially preventing, or minimizing, temperature changes in onedetector from affecting the temperature in adjacent detectors. In otherwords, the detector size and shape may be selected for desiredcharacteristics, for example, selected to provide sufficient pixelthermal isolation for the operating environment, given the anticipatedambient temperature, or the wavelengths being used for conditioning anddetecting.

FIG. 3 is a cross sectional view of the FIG. 2 embodiment of a focalplane array 16 taken along the line 3-3 in FIG. 2. As shown in FIG. 3,the focal plane array 16 includes a substrate 24. Disposed on thesubstrate are an array of detectors 266. As shown in FIG. 3, theperforations 264 will segment, or separate, the individual detectors266. As discussed in relation to FIG. 2, the cut-out regions, orperforations 264, of the focal plane array 16 provide thermal isolationbetween the individual detectors 266.

Various techniques can be used to produce the focal plane array 16 asillustrated in FIG. 3. For example, a substrate 24 can be provided, andthermal detector material may be disposed on the substrate 24. Forexample, the thermal detector material may be sprayed onto the substrate24, or it may be rolled onto the substrate, or sputtered onto thesubstrate 24, or any other techniques as will be known to those skilledin the art. After the thermal detector material has been disposed ontothe substrate, various techniques may be used to remove portions toprovide the cut-out regions 272. For example, a cutting source, such asa laser beam, may be used to cut away the material between the detectors266 and produce the perforated pattern between the detectors 266. Othertechniques may also be used to produce the perforated pattern, such asetching, photolithography techniques, cutting blades, or others thatwill be known to those skilled in the art.

FIG. 4 is a cross sectional view of another embodiment of a focal planearray 16. As shown in FIG. 4, the focal plane array 16 includes asubstrate 24 and an array of detectors 282 disposed on the substrate. Inthe embodiment illustrated in FIG. 4, cutaway regions 284 are locatedbetween the individual detectors 282 but the substrate underlying thecutaway regions 284 remains. In the example illustrated in FIG. 4, thethermal material between detectors 282 is removed so that thermalconnection between individual detectors 282 is limited to being throughthe substrate 24.

FIG. 5 is a plan view of a focal plane array 16 illustrating anembodiment of a focal plane array 16 as described in FIG. 4. As shown inFIG. 5 the array includes a substrate 24 and an array of detectors 282.In the FIG. 5 embodiment, no thermal material is transferred betweenadjacent detectors 282, but the substrate 24 is substantially continuousso as to provide mechanical support of the array of detectors 282. Inone embodiment, the substrate can be continuous, in other embodiments,portions of the substrate may be removed, for example, portions of thesubstrate between the individual detectors may be removed, or portionsof the array under the individual detectors 292 may be removed, or anyother combinations of removing and leaving the respective layers. In theembodiment illustrated in FIG. 5, using appropriate materials for thesubstrate, the array of detectors 282 can be thermally isolated fromeach other.

Various techniques can be used to produce the focal plane array 16 asillustrated in FIG. 5. For example, a substrate 24 can be provided. Uponthe substrate 24 thermal detector material may be disposed. For example,the thermal detector material may be sprayed onto the substrate 24, orit may be rolled onto the substrate, or sputtered onto the substrate 24,or any other techniques as would be known to those skilled in the art.After the thermal detector material has been disposed onto thesubstrate, various techniques may be used to remove the thermal detectormaterial so as to form the array of detectors 282. For example, acutting source, such as a laser beam, may be used to cut away thematerial between the detectors 282, while leaving the substrate 24substantially unchanged, and thereby produce the array of detectors 282.Other techniques may also include use of a mask, such as a wire mesh,that defines a desired pattern and is placed on the substrate prior toapplication or deposition of the thermal detector material. After thethermal detector material has been disposed, the mask may be removed,thereby also removing the corresponding thermal detector material, andproducing the array of detectors 282. In addition, techniques such asthose used in the manufacture of semiconductors, such asphotolithography techniques, may be used to remove portions of thethermal detector material to produce the array of detectors 282. Thedetectors can include materials as discussed previously.

FIG. 6 is a cross sectional view of an embodiment of a focal plane array16. As shown in FIG. 6, the focal plane array 16 includes a substrate 24and an array of detectors 300. An individual detector 300 may include aradiation sensitive layer 32 disposed upon the substrate 24. On the sideof the radiation sensitive layer 32 opposite the substrate, the detector300 may include a thermal conversion material 34, also referred to as anabsorber material.

FIG. 7 is a cross sectional view of an embodiment of a focal plane array16. As shown in FIG. 7, the focal plane array 16 includes a substrate 24and an array of detectors 310. An individual detector 310 may include athermal conversion material layer 34, or absorber, disposed on thesubstrate 24. On the side of the thermal conversion material layer 34opposite the substrate, the detector 310 may include a radiationsensitive layer 32.

FIG. 8 is a cross sectional view of yet another embodiment of a focalplane array 16. As shown in FIG. 8, the focal plane array 16 includes asubstrate 24 and an array of detectors 320. An adhesive layer 322 isdisposed on the substrate 24. A radiation sensitive layer 32 may bedisposed on the adhesive material 322. On the side of the radiationsensitive layer 32 opposite the substrate, the detector 320 may includea thermal conversion material, or absorber 34. In other embodiments, thethermal conversion material 34 may be disposed on the adhesive layer 322and the radiation sensitive layer 32 may be disposed on the thermalconversion material 34, opposite the substrate 24.

In previous embodiments described above, thermal isolation was achieved,at least in part, by separated detectors in a common plane. FIG. 9 is anelevation view of another embodiment of a focal plane array 16 in whichthe detectors are in different planes. As shown in FIG. 9, a detectorarray includes a substrate 330 and two arrays of detectors 332 and 334.As illustrated in FIG. 9, adjacent detectors 332 and 334 are located indifferent planes. That is, one set of detectors 332 has an outer surfacethat is at a different distance from the substrate 330 as compared withthe other set of detectors 334. Separation of the individual adjacentdetectors into different planes provides thermal isolation between thetwo sets of detectors 332 and 334. An advantage to the focal plane arrayof FIG. 9 is that it increases the active area of the focal plane arrayby decreasing the lateral separation between pixels.

FIG. 10 is a plan view of an embodiment of a focal plane array providingincreased active area. As shown in FIG. 10, the focal plane array 16includes a substrate 342 and a first array of detectors 332, illustratedin black, and a second array of detectors 334, illustrated in crosshatching. The first and second arrays of detectors 332 and 334 can beproduced, in one example, as shown in FIG. 9. That is, the first arrayof detectors 332 can be located in one plane, and the second array ofdetectors 334 can be located in a different plane. The separationbetween the two planes provides thermal isolation between individualdetectors. As shown in FIG. 9, arranging arrays of detectors ondifferent planes may be used to maximize the active array of the focalplane array 16.

FIG. 11 is an isometric illustration of an exemplary embodiment of afocal plane array 16. As shown in FIG. 11 the focal plane array 16includes a substrate 24. In the example illustrated in FIG. 11, thesubstrate 24 is generally the shape of a rectangular slab. Protrudingoutward from a top surface 26 of the slab are a plurality of columns 28.As described further below, on the top surface 30 of each column 28 aradiation detector is disposed. In this way, each of the columns withthe disposed detector corresponds to an individual mapping element, orpixel, of the focal plane array 16.

The columns 28 provide physical support for disposing a radiationdetector. Each column 28 also provides thermal isolation between thedetectors and the substrate 24. The thermal conductance of the columnmay be selected to be a desired value. For example, it may be desirablefor the column to have a low thermal conductance to thereby provide ahigh thermal isolation between the detectors and the substrate. But, itmay also be desirable to have the column thermal conductance high enoughso that there is a thermal path from the detector to the substrate 24allowing the detector to “bleed off” heat to the substrate when a sourceof radiation causing the detector to heat is removed. In other words, itmay be desirable to select the thermal conductance of the column to be avalue that allows a desired amount of beat transfer between theradiation detector and the substrate. This technique may also be used tochange the response time of the radiation detection sensor to changes inradiation.

As described further below, the location of the columns 28 relative toone another provide radiant and thermal isolation between individualdetectors within the array. There are several tradeoffs to consider inthe placement of the columns 28. For example, it is desirable to havethe detectors close to each other to increase the active area of thefocal plane area, the portion of the focal-plane array covered bydetectors, so as to increase resolution. However, it is also desirableto have the columns and detectors separated from adjacent columns anddetectors to increase isolation between adjacent detectors and reduce“bleeding” of signals between adjacent detectors. “Bleeding” can havethe effect of blurring high contrast detail in the image.

In one embodiment, a radiation detection sensor includes a thermalconversion material that converts radiation into heat energy. The sensoralso includes a plurality of mapping elements, or detectors, located onthe tops of the columns 28 shown in FIG. 11. Each of the mappingelements, or detectors, receives heat energy from the thermal conversionmaterial, thereby creating a thermal map corresponding to the radiationenergy. In another embodiment, individual pieces of thermal conversionmaterial are associated with individual detectors.

One embodiment of a radiation detection system using the describedradiation detection sensor, includes receiving radiated energy from anobject. The received energy is converted into thermal energy. Then areceived thermal energy map of the object is produced.

FIG. 12 is a cross sectional view of one embodiment of a focal planearray 16. As shown in FIG. 12, the focal plane array 16 includes asubstrate 24 that has columns 28 protruding from a top surface 26 of thesubstrate 24. On the top surface 30 of the columns 28 a detector 31 isdeposed. In the exemplary embodiment illustrated in FIG. 12, thedetector 31 includes a radiation sensitive layer 32. In one embodiment,the radiation sensitive layer is a thermochromic liquid crystal (TLC).In another embodiment the radiation sensitive layer 32 may be mixtures,of blends, of TLC materials with one or more configurations, or rangesof sensitivities. For example, two different TLCs with differentred-onset temperatures may be combined within a single detector. Inother words, different combinations of TLC materials may be used toconstruct a radiation sensitive layer with desired characteristics.

In the embodiment of FIG. 12, placed on top of the radiation sensitivelayer 32 is a thermal conversion material 34, commonly referred to as anabsorber, that converts radiation into heat energy. The absorber 34converts radiation that impinges upon it into thermal energy that issensed by the radiation sensitive layer 32. The absorber may be made ofblack cupric oxide. In general, absorbers may be made of any materialthat has high absorptivity and low emissivity characteristics. Inaddition, it is noted that absorber material may be transparent to someradiation while absorbing other radiation. For example, glass may absorbinfrared radiation even while it is nearly transparent to radiation inthe visible part of the spectrum. Although the absorber has beendescribed as converting radiation into thermal energy, the absorber maybe constructed of any type of material that converts radiation into aphysical characteristic that can be sensed by the radiation sensitivelayer.

In one embodiment, the focal plane array illustrated in FIG. 12 isconstructed using an optically transparent material for the substrate 24and the columns 28. Constructing the substrate 24 and the columns 28 ofoptically transparent material allows the sensing element to be viewedfrom the “back” 36 of the focal plane array, as described further below.

FIG. 13 is a cross sectional view of another embodiment of a focal planearray 16. The embodiment of the focal plane array 16 illustrated in FIG.13 is similar to that illustrated in FIG. 12 except that the absorber 34is placed on the top 30 of the column 28. The radiation sensitive layer32 is disposed on top of the absorber 34. Arranging the absorber 34 andradiation sensitive layer 32 in this manner allows the detector 31 to beviewed from the “front” 38 of the focal plane array as described furtherbelow.

FIG. 14 is a cross sectional view of yet another embodiment of a focalplane array 16. In the embodiment of the focal plane area illustrated inFIG. 14, the columns 28 have an expanded area forming the top surface 30of the column. Having an expanded top surface 30 on the column helps toincrease the active area of the focal plane area while providingincreased separation 502, and therefore increased isolation, between theregions of the columns 28 beneath the expanded top surface 30. Anexpanded top surface 30 supports a larger absorber area therebyincreasing the received irradiance per pixel. In general, an increase inthe irradiance per pixel increases the signal level thereby improvingthe signal to noise ratio (SNR) of individual detectors. In addition, anarrow column can provide a lower thermal conductance path and therebyimprove thermal isolation between the detectors and the substrate.

FIG. 15 is a schematic diagram illustrating additional aspects of aportion of the focal plane array 16. In the example in FIG. 15, thefocal plane array 16 is configured with a detector 31 disposed onto thetop surface 30 of a column 28. In the embodiment illustrated in FIG. 15,an absorber 34 is placed on top of a radiation sensitive layer 32.Radiation 52 that impinges onto the absorber 34 is converted intothermal energy. As the intensity of the radiation 52 onto the absorber34 increases, the thermal energy produced by the absorber increases.Likewise, as the intensity of the radiation 52 onto the absorber 34decreases, the thermal energy produced by the absorber decreases. Theradiation sensitive layer 32 detects the level of thermal energy of theabsorber 34.

The column 28 provides a low thermal conductance path, i.e. a highthermal isolation path, from the detector 31 to the substrate 24. Thelow thermal conductance path provides thermal isolation between thedetector and the substrate. The separation 64 between the detectors 31,provided by placement of the columns 28, provides thermal and radiantisolation between individual detectors within the focal plane array 16.The thermal and radiant isolation provided by the separation betweencolumns 28 may be provided in many different ways. In one embodiment,the focal plane array 16 can be located within an enclosure that hasbeen evacuated of a substantial portion of air so as to produce a deepvacuum. In another embodiment, the separation 64 between the columns 28may be made of a low thermal conductance materials, such as, aerogelmaterial.

In another embodiment, the relative positions of the radiation sensitivelayer 32 and absorbers 34 may be changed, as illustrated in FIG. 13. Inthis embodiment the radiation 52 would pass through the layer 32 andimpinge on the absorber 34 which would generate heat that is sensed bythe layer 32. The remaining thermal characteristics would be similar tothose described in relation to the embodiment of FIG. 14.

FIG. 16 is a cross sectional view of another embodiment of a focal planearray 16. FIG. 16 includes thermal shunts 72 between the top surface 26of the substrate 24 and the base 74 of the column 28 The thermal shunt72 may provide controllably variable thermal conductance paths. Forexample, the thermal shunts 72 may operate in different states. In onestate the thermal shunt 72 may operate to provide a low thermalconductance path, i.e. a high thermal isolation, between the substrate24 and the column 28. In another state, the thermal shunt 72 may operateto provide a high thermal conductance path, i.e. a low thermal isolationpath, between the substrate 24 and the column 28. When the thermal shunt72 is included the column 28 may be constructed with a high thermalconductance material so that when the thermal shunt 72 provides a highthermal conductance path, the column 28 and sensor element 32 willquickly approach thermal equilibrium with the substrate 24. When thethermal shunt 72 provides a low thermal conductance path, the column 28and sensor element 32 will be thermally isolated from the substrate 24.

The thermal shunt 72 may be constructed of various types of materials.For example, thermoelectric cooler/heater material, such as bismuthtelluride, may be used as the substrate 24 with columns made of a lowconductance material sitting on top of the substrate 24. The thermalshunt 72 may also be constructed using carbon nanotubes and aferro-fluid. Operation of the shunt may be controlled in different ways.For example, if the thermal shunt is constructed of a thermoelectriccooler/heater material, it may be controlled by varying a currentthrough the material using typical electrical control circuits, as arewell known. If the thermal shunt is constructed of carbon nanotubes anda ferro-fluid, it may be controlled by a controllable magnetic orelectric field.

In other embodiments the relative positions of the radiation sensitivelayer 32 and absorbers 34 may be changed, as illustrated in FIG. 13.

FIG. 17 is a schematic diagram illustrating additional aspects of aportion of a focal plane array 16. The example in FIG. 17 illustratesthe focal plane array 16 configured with detectors 31 constructed with aradiation sensitive layer 32 disposed onto the top surface 30 of acolumn 28. An absorber 34 is placed on top of the layer 32. Radiation 52that impinges onto the absorber 34 is converted to thermal energy. Asthe intensity of the radiation 52 onto the absorber 34 increases thethermal energy produced by the absorber increases. Likewise, as theintensity of the radiation 52 onto the absorber 34 decreases the thermalenergy produced by the absorber decreases. The layer 32 detects thelevel of thermal energy of the absorber 34.

Between the base 74 of the column 28 and the top surface 26 of thesubstrate 24 there is a thermal shunt 72. As described in relation toFIG. 16, the thermal shunt 72 may be controllably operable in differentstates between conduction and isolation to provide a higher thermalconductance path, i.e. low thermal isolation, or a lower thermalconductance path, i.e. high thermal isolation. Operation of the thermalshunt 72 can be used to periodically set the detectors to a desired biaslevel.

For example, during an initial operation the thermal shunt 72 may be ina high thermal conductance state and thereby provide low thermalisolation between the substrate 24 and the column 28. In this state, thecolumn 28 and detector 31 will reach thermal equilibrium with thesubstrate 24. As explained further below, the substrate 24 can becontrolled to be at a desired temperature. In this manner the detector31 can be biased to a desired temperature. For example, if the radiationsensitive layer 32 is TLC it can be biased to a desired operating point,such as temperature of red onset for the particular TLC material. Afterthe detector 31 has been biased to a desired operating point the thermalshunt can be operated to change to a state of low thermal conductanceand thereby provide a high thermal isolation between the substrate 24and the column 28.

While the thermal shunt 72 is in its low thermal conductance it willprovide a high thermal isolation between the column and the substrate.With the thermal shunt in this state, any radiation that impinges ontothe absorber 34 will be converted to heat. Due to the high thermalisolation between the column 28 and the substrate 24, the heat willremain in the absorber and be sensed by the radiation sensitive layer32. In this manner the amount of radiation impinging on the absorber 34can be detected. Due to the high thermal isolation, even whenmomentarily blocking the impinging radiation, the absorber will remainat an elevated temperature and be sensed by the layer 32. It may bedesirable to periodically “reset” the detector 31 to the predeterminedbias operating point. To “reset” the detector 31, the thermal shunt 72can be operated to change states so that there is a high thermalconductance path, providing low thermal isolation, between the column 28and the substrate 24 so that the column 28 and detector 31 return tothermal equilibrium with the substrate. In this manner, the focal planearray 16 can be periodically set to a predetermined operating point.

In another embodiment the relative positions of the radiation sensitivelayer 32 and absorbers 34 may be changed, as illustrated in FIG. 13. Inaddition, in other embodiments the thermal shunt 72 may be located inother positions relative to the substrate 24, radiation sensitive layer32, and absorber 34. For example, the thermal shunt 72 may by locatedbetween the top surface 30 of the column 28 and the detector 31. Inanother example, the thermal shunt may be located on top of the focalplane array, or between the focal plane array and the entrance pupil ofthe detection system, such as within the collection optics 14, toprevent radiation from impinging onto the focal plane array.

FIG. 18 is a schematic diagram illustrating an exemplary arrangement ofcomponents of a radiation detector system 10. The system includes afocal plane array 16 that is configured according to any one of theembodiments described above and constructed such that the focal planearray 16 is optically transparent. With the focal plane arrayconstructed in this manner, the sensing element may be viewed from theback side 36 of the focal plane array (where “back” is relative to thecollection optics 14).

Thus, in FIG. 18, an image of an object 12 is focused onto the focalplane array 16 by the collection optics 14. The focal plane array 16 isilluminated by an illumination source 18. An image of the focal planearray 16 detectors is focused onto an image sensor element 22 by imagingoptics 20.

FIG. 19 is a schematic diagram illustrating additional detail of anexemplary arrangement of imaging components that may be used in aradiation detector. As shown in FIG. 19, imaging optics 20 includes abeam splitter 102 and an imaging lens 104. The output of illuminationsource 18 is reflected in the beam splitter 102 and directed toilluminate the back of the focal plane array 16. In the path between theillumination source 18 and the focal plane array 16 may be placed anoptional filter 105. The filter 105 may be configured to block radiationemitted from the illumination source that the detectors within the focalplane array would sense, while passing other radiation. For example, ifthe detectors are sensitive to heat, the filter 105 may be configured toblock infrared radiation but pass other radiation. In one embodiment,the filter 105 may be constructed of glass which blocks infraredradiation so as to minimize any disturbance, or influence, of theillumination source upon the focal plane array detectors while stillallowing the focal plane array to be imaged through the filter 21. Theillumination source 18 may be a broad or a narrow spectral output. Inaddition, the illumination source may be tunable. In one embodiment, theillumination source 18 may be made of one or more narrow band sources soas to be able to enhance specific response ranges of the detectors. Thatis, the illumination source may have one or more narrow band sources,such as narrow band LEDs, that output a spectrum matched to a specificspectral range of interest.

An image of the detectors of the focal plane array 16 passes through thefilter 105 and the beam splitter 102 and is focused onto the imagesensor 22 by the imaging lens 104.

FIG. 20 is a schematic diagram illustrating another exemplaryarrangement of components of a radiation detector 10. In the example ofFIG. 20, the focal plane array is configured according to any one of theembodiments described above and constructed such that the focal planearray 16 is may be viewed from the front side 38 of the focal planearray (where “front” is relative to the collection optics 14; compareFIG. 18).

Thus, in FIG. 20, an image of an object 12 is focused onto the focalplane array 16 by the collection optics 14. The front of the focal planearray 16 is illuminated by the illumination source 18. An image of thefocal plane array 16 detectors is focused onto a sensor element 22 byimaging optics 20. In this configuration, because the detectors of thefocal plane array 16 are directly viewed, rather than viewing thedetectors “through” the focal plane array substrate, the substrate andcolumns of the focal plane array may be constructed of non-transparentmaterial. An optional filter, not shown, may be placed betweenillumination source 18 and the focal plane array 16. The filter may beconfigured to block radiation emitted from the illumination source thatthe detectors within the focal plane array would sense, while passingother radiation.

FIG. 21 is a block diagram of another embodiment of a radiationdetection system 10. The block diagram of FIG. 21 is similar to FIG. 1in that an image of an object 12 is focused onto the focal plane array16 by collection optics 14. An illumination source 18 illuminates thefocal plane array 16 and an image of the focal plane array detectors isfocused onto image sensor 22 by imaging optics 20. FIG. 21 also includesan environmental control unit 122. In one embodiment, the environmentalcontrol unit 122 may control the temperature of the substrate to biasthe focal plane array 16 to a desired operating point. In anotherembodiment, the environmental control unit 122 may evacuate the regionaround the focal plane array 16 to create a deep vacuum. In otherembodiments, other environmental features may be controlled, forexample, controlling both temperature and vacuum, and controllinghumidity or any other combination of environmental aspects includingmagnetic field and electrical field environment.

The example of FIG. 21 also includes an image processor 124 and adisplay 126. Image processing techniques are well known in the art andmay be used to enhance the visual display presented on the display 126.For example, it may be desirable to re-map the color thermal outputoriginating in the focal plane array 16 to conform the output togenerally accepted color maps for features such as hue, saturation, andintensity (HSI). It may also be desirable to re-map the color thermaloutput for contrast enhancement, red-green-blue (RGB) analysis,geometric distortion correction, etc.

The image processor 124 may be configured to control the illuminationsource. The image processor may also be configured to control theenvironmental control unit 122. For example, the image processor 124 maycontrol the environmental control unit 122 so as to bias the focal planearray to a desired operating point.

FIG. 22 is a schematic diagram illustrating a plan view of an exemplarydesign of a focal plane array 16. As shown in FIG. 22, the focal planearray 16 includes a substrate 24 and an array 132 of support columns 28.In the example of FIG. 22, the support columns 28 have a circular crosssection. As described above, detectors may be disposed upon the tops ofthe support columns 28 in various configurations.

FIG. 23 is a schematic diagram illustrating a plan view of anotherexemplary design of a focal plane array 16. As shown in FIG. 23, thefocal plane array 16 includes a substrate 24 and an array 132 of supportcolumns 28. In the example of FIG. 23, the support columns 28 have atriangular cross section. As described above, detectors may be disposedupon the tops of the support columns 28 in various configurations. Anaspect to the triangular cross section of the support columns is thateach side of one of the triangular cross sectional columns is directedtoward, or facing, an apex, or point, of an adjacent column. In thismanner isolation between adjacent columns may be increased by minimizingthe surface areas exposed to adjacent support columns.

FIG. 24 is a schematic diagram illustrating yet another exemplary designof a focal plane array 16. As shown in FIG. 24, the focal plane array 16includes a substrate 24 and an array 132 of support columns 28. In theexample of FIG. 24, the support columns 28 have a hexagonal crosssection. As described above, detectors may be disposed upon the tops ofthe support columns 28 in various configurations.

As illustrated by FIGS. 22-24, the focal plane arrays can includesupport columns constructed in many different shapes. FIG. 256(comprising 25A, 25B, 25C, and 25D) includes four different examples ofdetector support column shapes.

FIG. 25A is a schematic diagram of a support column 28 with a circularcross section. As shown in FIG. 25A, the support column 28 is acylindrical column with a circular cross section. In one embodiment, aradiation sensitive layer or absorber may be disposed onto the topsurface 166 of the column 28. In another embodiment, there may be anoptional recessed cavity 162 (indicated by dashed lines) in the top ofthe column 28 where a radiation sensitive layer, an absorber (such as athermal conversion material), or both may be disposed. The recess 162can provide further insulation between adjacent columns to reducelateral dispersion of incident energy.

FIG. 25B is a schematic diagram of another support column 28 with acircular cross section. As shown in FIG. 25B, the support column 28 hasa cylindrical base column 164 with an extended circular cross sectiontop 166 that has a larger diameter than the cylindrical base column 164.The cylindrical base column can be constructed as a solid, or as ahollow structure. In one embodiment, a radiation sensitive layer orabsorber may be disposed onto the top surface 166 of the column 28. Inanother alternative, a recessed cavity 162 (indicated by dashed lines)is located in the top surface 166 of the column 28, where the radiationsensitive layer, absorber, or both may be disposed. As noted above, inthe discussion of FIG. 14, the support column illustrated in FIG. 25Bmay increase the active area of the focal plane array while alsoincreasing the isolation between adjacent detectors. As noted, theisolation can be improved by the recess cavity 162 in the columns.

FIG. 25C is a schematic diagram of yet another support column 28. Asshown in FIG. 25C, the support column 28 may have a cylindrical basecolumn 164. In other embodiments, the base column may have solid,hollow, or structural aspects. The base column 164 can have other crosssectional shapes, for example, oval, or multisided polygons such astriangles, squares, rectangles, pentagons, hexagons, etc. Similarly, thecolumn construction may be constructed to have top surfaces of suchvaried shapes and configurations, including circular, oval, ormultisided polygons. In the example of FIG. 16C, the top surface 166 ofthe support column 28 has a triangular cross section. In one embodiment,a radiation sensitive layer or absorber may be disposed onto the topsurface 166 of the column 28. In another embodiment, there may be arecessed cavity 162 (indicated by dashed lines) in the top surface 166of the column 28 where the radiation sensitive layer, absorber, or bothmay be disposed.

In the examples shown in FIGS. 25A-25C, the recess 162 was the samecross sectional shape as the corresponding support column 28 (in FIG.16A), or the top surface 166 (in FIG. 25B and FIG. 25C). In otherembodiments, the recess 162 may be a different shape than thecorresponding top surface of the column. FIG. 25D is still anotherembodiment of a support column 28, this one having different recess andtop surface shapes. FIG. 25D is similar to FIG. 25C, where the supportcolumn 28 has a cylindrical base column 164 and the top surface 166 ofthe support column 28 has a triangular cross section. In FIG. 25D,however, the recess 162 is not the same cross section as the top surface166. As shown in FIG. 25D, even though the top surface 166 is one crosssectional shape, a triangle, the recess 162 may be a different crosssectional shape, for example an oval, as shown in FIG. 25D, or therecess may be any other desired shape.

In the examples illustrated in FIGS. 25A-25D the base support column wasdescribed as having a circular cross section. Other cross sections ofthe base support columns are possible. For example, the base supportcolumn may be oval, or any polygon shape.

FIG. 26 is a schematic diagram of an embodiment of a non-planar focalplane array 16. In the embodiment of FIG. 26, the substrate of the focalplane array 16 may be made of a pliable material such as polyester. Ifthe substrate 24 material is pliable, the focal plane array can beformed to shapes other than flat surface shapes. Likewise, the substrateof the focal plane array 16 can be formed to a non-planar shape even ifthe substrate is a non-pliable material. For example, as illustrated inFIG. 26, the focal plane array 16 is formed into a concave shape. Theconcave shaped focal plane array can be constructed using a non-pliablematerial that has been “shaped” into a concave form, or it can beconstructed using a pliable material that is “formed” into a concaveform. A concave shape of the focal plane array 16 may be desired in someapplications. For example in a reflective system, such as illustrated inFIG. 20, it may be beneficial to have a concave shaped focal plane array16. Also, if the object emitting the radiation is small in size, such asin microscopy applications, then it may be possible to improve theresolution, and detail, of the mapping of the radiation.

An additional aspect of making the focal plane array a concave shape isthat the separation 172 between the detectors 31 is decreased, therebyincreasing spatial resolution of the focal plane array. In addition, theseparation 174 of the support columns 28 is increased, thereby improvingisolation between adjacent columns 28.

FIG. 27 is a schematic diagram of another embodiment of a non-planarfocal plane array 16. In the embodiment of FIG. 27, the substrate of thefocal plane array 16 may be made of a pliable material such aspolyester. If the substrate 24 material is pliable, the focal planearray can be formed to shapes other than flat surface shapes. Likewise,the substrate of the focal plane array 16 can be formed to a non-planarshape even if the substrate is a non-pliable material. For example, asillustrated in FIG. 27, the focal plane array 16 is formed into a convexshape. The convex shaped focal plane array can be constructed using anon-pliable material that has been “shaped” into a convex form, or itcan be constructed using a pliable material that is “formed” into aconvex form. A convex focal plane array 16 may be desired in someapplications, such as, in the scenario where an object emittingradiation is large in size relative to the focal plane array. A convexfocal plane array 16 may also be desirable, for example, if a “fish-eye”lens is used in the collection optics.

FIG. 28 is a schematic diagram of an yet another embodiment of anon-planar focal plane array 16. The support columns of the focal planearray 16 in FIG. 28 have an enlarged top surface 30. Again, the focalplane array can be “shaped” or “formed” to shapes other that flatsurface shapes. For example, the focal plane array 16 in FIG. 28 has aconcave shape. Again, making the focal plane array a concave shape theseparation 172 between the detectors 31 is decreased, thereby increasingspecial resolution of the focal plane array. In addition, the separation174 of the support columns 28 is increased, thereby improving isolationbetween adjacent columns 28.

FIG. 29 is a schematic diagram of still another embodiment of anon-planar focal plane array 16. The support columns of the focal planearray 16 in FIG. 29 have an enlarged top surface 30. The focal planearray can be “shaped” or “formed” to shapes other that flat surfaceshapes. For example, the focal plane array 16 in FIG. 29 may formed intoa convex shape.

The shapes of the focal plane array illustrated in FIGS. 26-29 aremerely examples. The focal plane array can be “shaped” or “formed” intoother shapes, for example, hyperbolic, circular, spherical, etc. Inother words, the shape of the focal plane array can be selected asdesired for use in a particular application. The ability to have a focalplane array of different shapes can reduce, or eliminate, the need forexpensive optics needed to focus an image onto a planar focal planearray. In addition, the focal plane array may be constructed in a largeformat, for example, in a health care application it may be desirable toconstruct a focal plane array that is large enough to image an area ofinterest, such as a human face. Constructing a focal plane array in alarge format may allow the focal plane array to be directly viewedwithout the need for an imaging sensor or imaging optics.

FIG. 30 is a block diagram of an embodiment of an environmental controlunit. As shown in FIG. 30, temperature elements 212 are in thermalconnection with the substrate 24 of a focal plane array 16. A controller214 is connected to the temperature element 212 so as to adjust thetemperature of the temperature element 212. As the temperature of thetemperature element 122 varies the temperature of the focal plane array16 substrate 24 varies accordingly. In this way the focal plane arraysubstrate 24 can be set to a desired temperature. Also, in thermalconnection with the substrate 24 is a temperature sensor 216 thatdetects the substrate 24 temperature. The thermal sensor 216 is incommunication with the controller 214 thereby providing the substrate 24temperature for use by the controller 214 in controlling the temperatureelements 212. As described above, control of the substrate temperaturecan be used to bias some detectors, such as TLC, to desired operatingpoints, such as red onset, or some other point in their operating range.

The temperature element 212 may be any type of heating or coolingapparatus that can be controlled. For example, the temperature element212 may be a thermoelectric cooler, an electric heating element, orother device capable of controlling temperature. The embodiment of FIG.30 describes controlling the temperature of the substrate. Otherembodiments of an environmental control unit may control otherenvironmental characteristics. For example, the environmental controlunit may operate to maintain a desired temperature, or vacuum, orhumidity level or control any combination of environmentalcharacteristics including magnetic field and electric fieldenvironments.

FIG. 31 is a block diagram of a null sensor 221 arrangement. As shown inFIG. 31, an image of an object 12 passes through a beam splitter 222 andis focused onto a focal plane array 16 by collection optics 14. Thefocal plane array 16 is illuminated by illumination source 18. An imageof the detectors of the focal plane array 16 is focused onto imagesensor 22 by imaging optics 20. The output of the image sensor 22 isinput to an image processor 224. The output of the image processor maybe presented on a display 226. The image processor 224 is also incommunication with a controllable radiation source 228 and anenvironmental control unit 122 controlling a bias operating point of thefocal plane array.

In one embodiment, the focal plane array 16 includes sensing elements,such as TLC. The environmental control unit may be controlled by theimage processor 224 to establish a desired bias, or operating point forthe focal plane array 16. For example, the environmental control unit122 may establish a bias point for TLC detectors included on the focalplane array so that the TLC detectors are at red onset. Thus, with noradiation impinging upon the focal plane array, the entire array ofsensing elements would be biased to red onset. The elimination ofradiation impinging onto the focal plane array may be accomplished inmany ways, for example, placing a shutter over the entrance pupil of thenull sensor 221, or have thermal shunts located so as to block radiationfrom impinging on the focal plane array as described above.

After the focal plane array 16 has reached its bias operating point, thecontrollable radiation source 228 may be commanded to output radiationthat is reflected off of the beam splitter 222 so as to impinge upon thefocal plane array 16. The radiation from the controllable radiationsource 228 that impinges the focal plane array 16 is controlled so as toset the detectors in the focal plane array to a known, desired,operating point. For example, if the detectors include TLC, thecontrollable radiation source may be commanded by the image processor224 to input radiation sufficient to set the detectors in the focalplane array to green, or other desired, operating point. It is notedthat the controller radiation source 228 may include a scanningmechanism to scan the radiation source output across the focal planearray 16. In other embodiments the scanning mechanism may be separatefrom the controllable radiation source 228.

During operation of the null sensor 221, as radiation from the object 12impinges on the focal plane array the detectors that include TLC colorwill change accordingly. The change in color will be detected at theimage sensor 22. The output of the image sensor 22 is connected to theimage processor 224 that generates commands to the controllableradiation source to increase or decrease the output of the controllableradiation source as it scans across the focal plane array so that theTLC color remains at its desired operating color, for example green. Thesignal for controlling the controllable radiation source 228 correspondsto the radiation received from the object 12. The image processor 224may generate an image corresponding to the control signal and generate adisplay be presented on the display 226.

The description of FIG. 31 was of an embodiment when the “back” of thefocal plane array 16 is imaged. In another embodiment, rearrangement ofcomponents within the null sensor 221 can support imaging of the “front”of the focal plane array 16.

The controllable radiation source 228 may also be used to output a knownradiation directed to the focal plane array to characterize, orcalibrate, the sensitivity and response of detectors with the focalplane array. For example, the controllable radiation source 228 may becontrolled so as to expose the focal plane array 16 to a constantradiation level, a step change in radiation level, a gradient radiationlevel, or other variable radiation level. In addition, a target with aknown radiation profile may be exposed to the focal plane array 16. Forexample a target “shutter” may be placed in front of, or in the entrancepupil of, the radiation detector system and thereby be exposed to thefocal plane array. The performance of the detectors within the focalplane array when exposed to a known radiation can be evaluated. Forexample, the performance characteristics of the detectors, such assensitivity and response to a step, or varying radiation input can beevaluated.

FIG. 32 is a block diagram of another embodiment of a radiation detectorsystem. As shown in FIG. 32 the radiation detection system includes apressure vessel 232. One end of the pressure vessel 232 allows radiationto enter the vessel. For example, one end of the pressure vessel 232 maybe formed by at least a portion of the collection optics 14 thatincludes a glass plate, or lens, that forms the end of the pressurevessel. Inside the pressure vessel is a focal plane array 16. Alsolocated in the pressure vessel is a temperature control unit 234. Forexample, the temperature control unit 234 may be constructed so as to benear or in contact with the back of the focal plane array 16. Asdescribed above, the temperature control unit may be used to bias thefocal plane array to a desired operating temperature.

In the example shown in FIG. 32, also located in the pressure vessel areimaging optics 20 and an imaging sensor 22. The imaging optics 20 focusan image of the focal plane array onto the imaging sensor. In anotherembodiment, at least a portion of the imaging optics 20 includes a glassplate, or lens, that forms another end of the pressure vessel 232. Inthis way, the imaging sensor 22, as well as additional optics, may belocated external to the pressure vessel 232. Penetrating the pressurevessel 232 is a port 236 for the pressure control of the internalenvironment. This port allows the pressure vessel 232 to be pressurized,or to have a, vacuum drawn within the pressure vessel.

FIG. 33 is a schematic illustrating another embodiment of a radiationdetection system 240. The radiation detection system 240 in FIG. 33 issimilar to the radiation detection system 10 illustrated in FIG. 18 andincludes an object 12, collection optics 14, focal plane array 16,illumination source 18, imaging optics 20 and imaging sensor 22. Theradiation detection system 240 illustrated in FIG. 33 includes a targetillumination source. The target illumination source 242 illuminates, or“paints”, the object 12. Radiation reflected from the object 12 is thencollected by collection optics and focused onto the focal plane array.The target illumination source 242 may be tunable. For example, thetarget illumination source 242 may include optics or controls to shapethe spectrum, such as the color and geometry, of the radiation output bythe target illumination source 242. In another example, the targetillumination source 242 may include multiple sources, each of whichoutputs a desired spectrum of radiation. In one embodiment, the outputof the multiple sources may be mixed, or combined, in any desiredcombination into a composite source with a desired output spectrum. Inanother embodiment, the sources may be multiplexed so that only desiredones of the sources, or individual sources, are on at any given moment.

In this manner the object may be painted with radiation of a desiredspectral content which may improve the detection of specific objects.For example, if it is desired to identify a particular object, thetarget illumination source 242 may have its spectral output configuredsuch that radiation that will be reflected from the object of interestwill be increased.

The radiation detection system 240 may also include an input filter 244.The input filter may be configured to pass a desired spectrum. Forexample, the input filter 244 may be configured to have a spectralresponse, that is pass spectral energy, matched to the spectral outputof the target illumination source 242. In another example, the inputfilter may be configured to have a spectral response that matches aspectral profile of a specific object. The input filter 244 may also betunable, that is its spectral response may be configurable. In otherembodiments, the input filter 244 may include multiple filters that ateindividually, or in combination, used to produce the desired spectralresponse.

FIG. 34 is a flow chart illustrating detection of radiation from anobject. Flow begins in block 252 where radiation emitted from an objectis collected. For example the object may be viewed with collectionoptics that gather, and form, the radiation in a desired way. In block254 the collected radiation is focused onto a focal plane array. Forexample, the collection optics can collect the radiation emitted from anobject and focus the radiation onto the focal plane array. The focalplane array may include a plurality of detectors that are formed in anarray upon the focal plane array. In block 256 the array of detectorsare imaged. For example, an imaging sensor, such as a camera, mayproduce an image of the array of detectors.

For example, if the detectors include TLC, so that the individualdetectors change color in relationship to the amount of radiation thatimpinges on them, then an image of the detector array can be used to mapthe radiation that was emitted by the object.

FIG. 35 is an elevation view of another exemplary embodiment of a focalplane array 16. As shown in FIG. 35 a substrate 24 has an array ofcolumns 3502 and 3504 protruding from a surface of the substrate. Uponthe top of each column is a detector 31. In the embodiment of FIG. 35 afirst array of columns 3502 are a different height than a second set ofcolumns 3504. Because the columns are different heights, they can belocated so that the physical spacing between the detectors 31 when viewfrom the top 3506 is minimized. As shown in FIG. 35, if the detectors 31cross sectional area is larger than the cross section of the columns3502 and 3504, the detectors 31 may be located such that they overlaywhen viewed from the top 3506. In this manner, the active area of thefocal plane array can be maximized.

In the embodiments described the focal plane array has included asubstrate. In other embodiments, the focal plane array does not need toinclude a substrate. For example, the thermal detector material may becontinuous and patches of absorber material may define the detectors.Likewise, an absorber material may be continuous and thermal detectormaterial disposed upon the absorbed thereby defining detectors. In otherwords, the substrate is simply a means for supporting the detectors, andit is possible to made a focal plane array with one of the otherelements, i.e. detector, or absorber, performing the supportingfunction.

In addition, while some embodiments have described examples of detectorsas including a thermal detecting material and an absorbed, they are notlimited to this type of detector. That is, exemplary detectors map oneform of energy to another form of energy. For example, a detector may beany device that performs the function of mapping thermal energy to avisual display.

In general, a radiation detection sensor can include a radiationdetector on a substrate. The radiation detector may be segmented into anarray of mapping elements, or detectors, such that individual mappingelements are substantially thermally isolated from each other andcomprise pixels of a visual thermal energy map. The radiation detectionsensor may have the radiation detectors within the array of mappingelements minimally connected to adjacent radiation detectors.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

1. A radiation detection sensor comprising: a radiation detector that issegmented into an array of mapping elements that are substantiallythermally isolated from each other and comprise pixels of a visualthermal energy map; and an image sensor that receives the visual thermalenergy map and produces a corresponding image.
 2. A radiation detectionsensor as defined in claim 1, wherein the array of mapping elementscomprises mapping elements that are minimally physically connected toadjacent mapping elements.
 3. A radiation detection sensor as defined inclaim 1, wherein the mapping elements of the radiation detector areformed by a substrate material and a thermal detection material.
 4. Aradiation detection sensor as defined in claim 3, wherein the mappingelements are defined by voids in portions of the thermal detectionmaterial.
 5. A radiation detection sensor as defined in claim 4, whereinthe voids are formed by perforations in the thermal detection material.6. A radiation detection sensor as defined in claim 1, wherein themapping elements are formed with micro-deposition techniques.
 7. Aradiation detection sensor as defined in claim 1, wherein the mappingelements of the radiation detector comprise a radiation sensitive layerand a thermal conversion material.
 8. A radiation detection sensor asdefined in claim 7, wherein the radiation sensitive layer is athermochromic liquid crystal material.
 9. A radiation detection sensoras defined in claim 7, wherein the thermal conversion material has highabsorptivity and low emissivity.
 10. A radiation detection sensor asdefined in claim 7, further comprising thermal elements that are used tocontrol a temperature of the substrate.
 11. A radiation detection sensoras defined in claim 10, wherein the thermal elements comprisethermoelectric coolers.
 12. A radiation detection sensor as defined inclaim 10, further comprising an environmental control unit.
 13. Aradiation detection system, comprising: a focal plane array thatincludes a radiation detector that is segmented into an array of mappingelements such that individual mapping elements are substantiallythermally isolated from each other and comprise pixels of a visualthermal energy map; collection optics that focus radiation emitted froman object onto the focal plane array; and imaging optics that focus animage of the focal plane array pixels onto an image sensor.
 14. Aradiation detection system as defined in claim 13, further comprising animage processor configured to accept graphics output from the imagesensor and provide an enhanced visual image.
 15. A radiation detectionsystem as defined in claim 14, wherein the image processor analyzes theoutput of the image sensor and generates a command for a controllableradiation source.
 16. A radiation detection system as defined in claim15, wherein the command for the controllable radiation source causes thecontrollable radiation source to output radiation that is directed tothe focal plane array and maintains the mapping elements at apredetermined value.
 17. A radiation detection system as defined inclaim 13, wherein the image sensor is a camera.
 18. A method ofdetecting radiation emitted from an object, the method comprising:focusing radiation emitted from an object onto a focal plane array,wherein the focal plane array includes a radiation detector that issegmented into an array of mapping elements such that individual mappingelements are substantially thermally isolated from each other andcomprise pixels of a visual thermal energy map; and focusing an image ofthe array of detectors onto an imaging sensor thereby producing an imageof the visual thermal energy map.
 19. An apparatus for detectingradiation emitted from an object; the apparatus comprising: means forfocusing radiation emitted from an object onto a focal plane array,wherein the focal plane array includes a radiation detector that issegmented into an array of mapping elements such that individual mappingelements are substantially thermally isolated from each other andcomprise pixels of a visual thermal energy map; and means for focusingan image of the array of detectors onto an imaging sensor therebyproducing an image of the visual thermal energy map.
 20. A method ofproducing a radiation detection sensor, the method comprising: providinga thermal detection material; and segmenting the thermal detectionmaterial into an array of mapping elements that are substantiallythermally isolated from each other and comprise pixels of a visualthermal energy map.
 21. A method as defined in claim 20, whereinsegmenting comprises removal of portions of the thermal detectionmaterial.
 22. A method as defined in claim 20, wherein the thermaldetection material includes a radiation detector material and substrate.23. A method as defined in claim 20, wherein segmenting comprisesremoving portions of the thermal detection material.
 24. A method asdefined in claim 20, wherein segmenting comprises micro-disposingthermal detection material into pixel-sized portions.
 25. A method asdefined in claim 24, wherein segmenting comprises photolithographyprocessing.
 26. A method as defined in claim 25, wherein segmentingcomprises depositing radiation detector material onto a substrate. 27.An apparatus for producing a radiation detection sensor, the apparatuscomprising: means for disposing a radiation detector material onto asubstrate; and means for segmenting the radiation detector material intoan array of mapping elements that are substantially thermally isolatedfrom each other and comprise pixels of a visual thermal energy map. 28.A method of producing a radiation detector, the method comprisingsegmenting a radiation detector material into an array of mappingelements such that individual mapping elements are substantiallythermally isolated from each other and comprise pixels of a visualthermal energy map.